1. Technical Field
This invention relates to telephone message systems and, more particularly, to a telephone message system which includes standard telephone equipment.
2. Description of the Prior Art
Various improvements have been made in residential telephone equipment by adding certain features and services. One such service is Caller ID wherein the identity of a calling party is made available to a called party prior to the called party answering an incoming telephone call. This advantageously allows a called party the option of screening calls and only answering those that he or she recognizes and chooses to answer. The Caller ID feature is described more comprehensively in U.S. Pat. No. 4,277,649.
Other improvements in residential telephone equipment include such features and services as: an intercom system for paging and monitoring; a facsimile machine and a computer for sending and receiving images and data, by way of example. Since one cannot expect to find more than a single wire-pair at any given location, it is frequently necessary to supply additional wiring beyond the single wire-pair used for basic telephone service in order to increase the number of communication channels. Costs associated with adding or relocating wires can be significant, however. Furthermore, many commercially available systems that are used to increase information distribution capacity are incompatible with existing telephone equipment, so a user's investment is immediately eroded.
From a convenience standpoint, it is desirable for a customer to merely purchase a telephone product, take it home, and plug it into an existing telephone jack. Many systems that utilize the local telephone wire-pair at a user's premises require that a master station be placed in a series connection with the incoming wire-pair from the telephone central office. Series connections require that internal wiring be modified which usually means that a telephone installer or an electrician needs to be hired. Series connections also have the drawback that the master station cannot be located at any telephone jack. Since the master station terminates the incoming wire-pair, it is typically located at the protector block or the telephone jack nearest to it. Relocating a master station presents difficulties because the connection must be electrically maintained at one point while the station is physically moved to another. Finally, even when the master station is compatible with existing telephone sets, should the master malfunction, series connected equipment is likely to malfunction as well.
It is therefore desirable to provide improved functions and features in telephone equipment for use at residential premises, yet have such equipment be compatible with and operate along with existing telephone extensions on a common wire-pair.